Chesapeake Bay continues to decline, despite the comeback of rockfish and reduced pollution from factories and municipal sewage plants, the Chesapeake Bay Foundation said today.

In a sweeping 288-page report on the state of the bay, the Annapolis environmental group concludes that "a decade of intense private and public effort to save the bay has averted immediate disaster."

But the Chesapeake is still losing ground to suburban sprawl that gnaws away at the bay's remaining forests and wetlands, robbing it of its ability to recover from the pollution that has degraded its waters.

The report, titled "Turning the Tide," calls for an immediate baywide moratorium on harvesting oysters, among other things, as well as more stringent pollution controls on farming and development and a cap on population growth in the bay region.

Those recommendations already are getting a chilly reception from farmers and fisheries officials, and watermen are sure to fight any move to ban oyster harvesting.

But William C. Baker, the bay foundation's president, contends that current efforts to save the bay are not nearly enough, given projections that nearly 3 million more people are expected to settle around the bay over the next 30 years.

"We can't just say we want the bay to be restored and not tackle the tough questions," Baker said in an interview. He suggested it is time for a new "summit" of state and federal officials to reassess the multistate bay cleanup effort agreed to at the last such meeting in December 1987.

Underwritten by a $160,000 grant from the Abell Foundation, the bay foundation report contains no new scientific findings, but instead draws on existing research to compile a layman's "report card" on the Chesapeake's condition, from the clarity of its water the abundance of its waterfowl.

The report, published by Island Press, was written by Tom Horton, a former environmental reporter for The Sun who now works for the bay foundation, and by William M. Eichbaum, a vice president of the World Wildlife Fund who helped launch the regional bay cleanup under Maryland Gov. Harry Hughes.

"Nearly eight years after the historic agreement to restore the bay's health made . . . in December 1983, there still is no discernible trend toward a systemwide comeback," the report concludes. "Progress too often is still of the variety that has been characterized as rowing ahead at four knots when the current is moving against us at five."

Spending hundreds of millions of dollars to upgrade sewage-treatment plants has helped restore water quality on portions of the Potomac and Patuxent rivers, the report acknowledges. And striped bass, or rockfish, have rebounded dramatically after a five-year fishing moratorium in Maryland and severe catch limits elsewhere along the Atlantic Coast.

But the report takes little satisfaction from such gains, noting that rockfish reproduced poorly again last year after the near-record 1989 spawn that prompted an easing of the baywide fishing ban.

And, even though blue crab harvests continue at near-record levels, the report notes that watermen are working much harder today to haul in the same catch, and there is no other seafood staple for them to fall back on if the crab populations do crash.

Oysters, once the backbone of the bay, are at an all-time low, the report notes, with stocks only 1 percent of what they were a century ago. And it suggests that officials spend as much on restoring oysters as they do on sewage treatment, noting that the shellfish naturally filter out the silt and nutrients that are degrading the bay's water.

The report also points out that:

* Underwater bay grasses, whose dramatic disappearance two decades ago signaled the bay's distress, seem to have recovered slightly in the last few years. But they still remain far below previous levels.

* Controlling pollution from agriculture, "a major source of the bay's water quality problems, is proving much more difficult and less effective than we had hoped."

The report calls for making pollution-control practices a condition of getting government agricultural subsidies, targeting problem farms for "immediate mandatory cleanups" and even requiring some livestock farmers to operate under discharge permits, as factories do.

* Sediment- and stormwater-control devices required for new development do not keep enough mud and pollution out of streams and the bay. About three-fourths of 90 construction sites surveyed in Maryland, Virginia and Pennsylvania were doing a poor job of keeping sediment from washing off the land, and only 10 percent were taking the pollutants out of stormwater runoff.

The foundation's report finds Maryland has done more than its neighbors, Virginia and Pennsylvania, particularly with its Critical Area and non-tidal wetlands laws. But it finds fault with Maryland as well, saying that no state has done enough yet to curb the sprawling growth that has gobbled up farmland, forests and wetlands.